When foreign matter becomes mixed into a glass body or when flaws in glass quality are brought about by changes due to heat, a so-called strain is produced in a container made of such glass material, with the result that the glass container is greatly reduced in quality. When a glass bottle having strain is used, for example, as a container for beverages, there is a possibility of the bottle being broken during use because of the strain, and particularly when such a glass bottle is used as a container subject to internal pressure, such a possibility is immensely increased. Also, when bubbles are produced in the glass of a glass container, the container is reduced in quality and strength.
In detecting foreign matter in a glass bottle, macrography by an examiner has heretofore been a general practice which however has various disadvantages such as lack of efficiency, variation in precision in examination due to a difference between examiners, reduced precision in examination, etc.
Although there exists automatic optical testers as a means for detecting foreign matter that has gotten mixed into the glass of a glass bottle, testers of this kind have the disadvantage that when the foreign matter is transparent or translucent or when an object to be examined such as a glass bottle is impressed with letters and characters in the form of, for example, raised letters, the irregular reflection and light-screening effects resulting therefrom act as a deterrent to detection of strain.
Known prior art in determining the quality of a glass bottle by an electric signal into which an optical state of the bottle is converted by use of a camera pickup tube includes Japanese Patent Publication No. 9998/1973. However, the art described therein requires a plurality of reflecting optical systems, does not provide sufficient monitoring, and also renders it difficult to make a speedy examination of a large number of bottles.
Devices using TV apparatuses are also known in the art. Generally, they all employ storage type pickup tubes and detect irregularities in glass by TV scanning immediately after temporarily storing (by means of an on-and-off light source like a flash lamp) a stationary image of only one side of an object on the photoelectric surface of a pickup tube. Thus, in order to examine the whole circumferential surface of an object, a plurality of TV cameras must be used in conjunction with a complicated control mechanism. Further, linear scanning and the following of an object at an optional speed, as used in this invention, are practically impossible by a storage type pickup tube due to the risk of burnt photoelectric surfaces or residual images.
Related prior art U.S. patents of which we are aware include Glasgow et al U.S. Pat. No. 1,934,187; Gray U.S. Pat. No. 2,073,691; Richards U.S. Pat. No. 2,798,605; and Wyman U.S. Pat. No.3,351,198. Each of the devices described in the foregoing patents, however, is subject to certain deficiencies which render the glass defect detecting apparatus therein described either inaccurate or imprecise. The Gray patent, for example, relies upon human visual observation for a readout, while the Glasgow et al patent is exemplary of a single-sided observation detection scheme, as discussed above. Further, the Richards patent provides no means for either synchronizing the movement of the object under inspection with the scanning lines, nor for ensuring that the entire surface of the object is inspected thoroughly and completely.